A reactor is one of the components of a circuit that performs a voltage step up or step down operation. For example, Patent Literature 1 discloses a reactor that is used for a converter mounted on a vehicle such as a hybrid vehicle. The reactor includes a sleeve-like coil, a magnetic core disposed inside and outside the coil, and a bottomed sleeve-like case storing the coil and the magnetic core. Patent Literature 1 discloses the mode in which the portion of the magnetic core that covers the outer circumferential face and end faces of the coil is made of a composite material of magnetic substance powder and resin.
The reactor used as an in-vehicle component is generally used as being fixed to an installation target such as a cooling base, such that the coil and the like that produce heat when being energized are cooled. The case is made of a material exhibiting excellent thermal conductivity, such as aluminum (see paragraph [0039] and others in the specification of Patent Literature 1). The case is fixed such that its outer bottom face is in contact with the installation target, to be used as a heat dissipation path.